1. Field of the Invention
The invention relates generally to a rack systems for housing animals.
2. Description of Related Art
It is well known in the art to house laboratory animals, such as mice and rats, in cages. It is also well known in the art to house the cages on racks. These cages are typically suspended from the shelf above the cage via a rim or flange that extends outward from the top of the cage. The cages can be designed such that they are placed without a cage top into the rack, and ambient air is permitted to enter into the cage. Other cages can be ventilated, and, when placed in a rack, environmentally controlled (e.g., air-flow and air exchange rate) by a fan or air supply system of the rack.
One such ventilated cage and rack system is disclosed in U.S. Pat. No. 6,158,387, assigned to Lab Products, Inc., in which a rack includes an air exhaust plenum and a canopy. The canopy is capable of supporting a cage within the rack above the canopy, and also positioning another cage below the canopy so as to permit air to be drawn into the air exhaust plenum from the interior of the second cage through the top of the second cage and to also permit ambient air to be drawn across the top of the second cage into the air exhaust plenum. Cages for such systems may be referred to as cage level barrier cages because they provide for a barrier between the interior and exterior of the cage such that contaminants from the interior of the cage do not readily leave the cage, and likewise, contaminants from the exterior of the cage do not readily enter the interior of the cage.
Other, non-ventilated racks are designed such that a cage hangs from or is otherwise positioned below a perforated shelf, so that air may pass through the shelf perforations and into a cage. In some instances, a filter which is placed on the perforated shelf, such that air is filtered as it passes through the perforations in the shelf and into a cage.
Such ventilated cage and rack systems were satisfactory. However, due to the manner in which the cage is positioned within the rack, only a single width of cage may be accommodated by the rack. Thus, certain racks were designed to house relatively wide cages, while other racks were designed to house relatively narrow width cages.
In some situations, however, personnel may benefit from the use of cages having different widths. This situation may arise when a study is performed using animals of different species or sizes. A larger animal, or different species of animal, may require a larger cage size than another. Additionally, for the purposes of a study, it may be desirable to house a larger number of animals in one cage than in another, consequently requiring different size cages. Furthermore, in some circumstances, a single cage size may be used, with a larger than needed cage being used for containing animals. This strategy, however, typically leads to a waste of valuable space. Additionally, two different racks may be used, each rack accommodating a different size cage, but again, this strategy also tends to lead to the wasting of valuable space. As such, a need exists for an improved ventilated cage and rack system.
Furthermore, it is undesirable to use an existing single cage size rack to house double racks. For example, one known method of retaining cages in a rack is the use of suspending brackets in each section in which the flanges on the top of cages can be inserted and retained in place. A typical double cage cannot be inserted in the place of two single cages because of the brackets in between the two sections. A modified double cage must be produced, which can cause further disadvantages. For example, the modified double cage can have a cut out where the brackets in between the sections can pass through. However, because most cages are made of plastic, cutting out a portion of the cage can weaken the cage. The cage can break, or bend in at the cut out because of the weight of the cage and its contents, ultimately leading to the cage falling off the rack.
Furthermore, the weight of the double cage would be resting on two brackets typically intended for single cages. Therefore, the extra weight may cause the brackets or the thin shelf above, from which the brackets extend, to bow. Because the double cage would be hanging on the brackets, the bow in the brackets or shelf may also result in the cage falling off the rack.
Accordingly, there is a need for a cage rack system that can overcome the deficiencies of known cage and rack systems.